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<div class="titlepage"><div><div><h4 class="title">
<a name="geometry.reference.algorithms.reverse"></a><a class="link" href="reverse.html" title="reverse">reverse</a>
</h4></div></div></div>
<p>
          <a class="indexterm" name="idm45246431642080"></a>
Reverses the points within a geometry.
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h0"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.description"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.description">Description</a>
        </h6>
<p>
          Generic function to reverse a geometry. It resembles the std::reverse functionality,
          but it takes the geometry type into account. Only for a ring or for a linestring
          it is the same as the std::reverse.
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h1"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.synopsis"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.synopsis">Synopsis</a>
        </h6>
<p>
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">reverse</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">)</span></pre>
<p>
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h2"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.parameters"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.parameters">Parameters</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Type
                  </p>
                </th>
<th>
                  <p>
                    Concept
                  </p>
                </th>
<th>
                  <p>
                    Name
                  </p>
                </th>
<th>
                  <p>
                    Description
                  </p>
                </th>
</tr></thead>
<tbody><tr>
<td>
                  <p>
                    Geometry &amp;
                  </p>
                </td>
<td>
                  <p>
                    Any type fulfilling a Geometry Concept
                  </p>
                </td>
<td>
                  <p>
                    geometry
                  </p>
                </td>
<td>
                  <p>
                    A model of the specified concept which will be reversed
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="geometry.reference.algorithms.reverse.h3"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.header"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.header">Header</a>
        </h6>
<p>
          Either
        </p>
<p>
          <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        </p>
<p>
          Or
        </p>
<p>
          <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">algorithms</span><span class="special">/</span><span class="identifier">reverse</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h4"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.conformance"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.conformance">Conformance</a>
        </h6>
<p>
          The function reverse is not defined by OGC.
        </p>
<p>
          The function reverse conforms to the std::reverse function of the C++ std-library.
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h5"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.behavior"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.behavior">Behavior</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Case
                  </p>
                </th>
<th>
                  <p>
                    Behavior
                  </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                  <p>
                    Point
                  </p>
                </td>
<td>
                  <p>
                    Nothing happens, geometry is unchanged
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Segment
                  </p>
                </td>
<td>
                  <p>
                    Not yet supported in this version
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Box
                  </p>
                </td>
<td>
                  <p>
                    Nothing happens, geometry is unchanged
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Linestring
                  </p>
                </td>
<td>
                  <p>
                    Reverses the Linestring
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Ring
                  </p>
                </td>
<td>
                  <p>
                    Reverses the Ring
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Polygon
                  </p>
                </td>
<td>
                  <p>
                    Reverses the exterior ring and all interior rings in the polygon
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Multi Point
                  </p>
                </td>
<td>
                  <p>
                    Nothing happens, geometry is unchanged
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Multi Linestring
                  </p>
                </td>
<td>
                  <p>
                    Reverses all contained linestrings individually
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Multi Polygon
                  </p>
                </td>
<td>
                  <p>
                    Reverses all contained polygons individually
                  </p>
                </td>
</tr>
</tbody>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
            The reverse of a (multi)polygon or ring might make a valid geometry invalid
            because the (counter)clockwise orientation reverses.
          </p></td></tr>
</table></div>
<h6>
<a name="geometry.reference.algorithms.reverse.h6"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.complexity"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.complexity">Complexity</a>
        </h6>
<p>
          Linear
        </p>
<h6>
<a name="geometry.reference.algorithms.reverse.h7"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.reverse.example"></a></span><a class="link" href="reverse.html#geometry.reference.algorithms.reverse.example">Example</a>
        </h6>
<p>
          Shows how to reverse a ring or polygon
        </p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">polygon</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">ring</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">adapted</span><span class="special">/</span><span class="identifier">boost_tuple</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="identifier">BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS</span><span class="special">(</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">cartesian</span><span class="special">)</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">assign</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">assign</span><span class="special">::</span><span class="identifier">tuple_list_of</span><span class="special">;</span>

    <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">tuple</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">point</span><span class="special">;</span>
    <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">polygon</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span> <span class="identifier">polygon</span><span class="special">;</span>
    <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">ring</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span> <span class="identifier">ring</span><span class="special">;</span>


    <span class="identifier">polygon</span> <span class="identifier">poly</span><span class="special">;</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">exterior_ring</span><span class="special">(</span><span class="identifier">poly</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">tuple_list_of</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">)(</span><span class="number">0</span><span class="special">,</span> <span class="number">9</span><span class="special">)(</span><span class="number">10</span><span class="special">,</span> <span class="number">10</span><span class="special">)(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">interior_rings</span><span class="special">(</span><span class="identifier">poly</span><span class="special">).</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">tuple_list_of</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">)(</span><span class="number">4</span><span class="special">,</span> <span class="number">6</span><span class="special">)(</span><span class="number">2</span><span class="special">,</span> <span class="number">8</span><span class="special">)(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">));</span>

    <span class="keyword">double</span> <span class="identifier">area_before</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">poly</span><span class="special">);</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">reverse</span><span class="special">(</span><span class="identifier">poly</span><span class="special">);</span>
    <span class="keyword">double</span> <span class="identifier">area_after</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">poly</span><span class="special">);</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">dsv</span><span class="special">(</span><span class="identifier">poly</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">area_before</span> <span class="special">&lt;&lt;</span> <span class="string">" -&gt; "</span> <span class="special">&lt;&lt;</span> <span class="identifier">area_after</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>

    <span class="identifier">ring</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">tuple_list_of</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">)(</span><span class="number">0</span><span class="special">,</span> <span class="number">9</span><span class="special">)(</span><span class="number">8</span><span class="special">,</span> <span class="number">8</span><span class="special">)(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span>

    <span class="identifier">area_before</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">r</span><span class="special">);</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">reverse</span><span class="special">(</span><span class="identifier">r</span><span class="special">);</span>
    <span class="identifier">area_after</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">r</span><span class="special">);</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">dsv</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">area_before</span> <span class="special">&lt;&lt;</span> <span class="string">" -&gt; "</span> <span class="special">&lt;&lt;</span> <span class="identifier">area_after</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>

    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
        </p>
<p>
          Output:
        </p>
<pre class="programlisting">(((0, 0), (10, 10), (0, 9), (0, 0)), ((1, 2), (2, 8), (4, 6), (1, 2)))
38 -&gt; -38
((0, 0), (8, 8), (0, 9), (0, 0))
36 -&gt; -36
</pre>
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